1. Field of the Invention
The invention relates to a swivel motor and particularly to a unit actuated by pressure medium.
2. Description of the Related Art
Pressure medium-actuated units are generally used to support a structural component part in an operating movement. In such cases, the structural component part can be subject to an external load. In a unit that is constructed as a swivel motor, in a vehicle chassis, a stabilizer arrangement can execute a swiveling movement but, due to deflection of the wheels of one axle, the swivel motor is exposed to a load of an appreciably higher frequency than the rocking movement of a vehicle body pressure changes in the pressure-medium supply.
In DE 10 2004 051 444 A1 pulsing of the pressure medium is discussed and by way of a solution a foam body is arranged in at least one work chamber of the unit. The foam body has at least one disadvantage in that the operating path of the unit is restricted. Further, it must be ensured that no decomposition occurs over the life of the unit which would release particles from the foam body that would clog the unit or the pressure supply system.
DE 10 2004 039 767 A1 discloses a swivel motor comprising a cylinder with ribs extending axially at the inner diameter, which cylinder is closed at the ends by two covers, a motor shaft with vanes having the same axial extension as the ribs of the cylinder, wherein the vanes of the motor shaft and the ribs of the cylinder, together with the cylinder, covers and motor shaft, form individual work chambers, a first and a second pressure medium connection for two work chambers separated in each instance by a rib, a join system between the work chambers which joins work chambers at least by pairs. The arrangement of the connected work chambers is carried out in such a way that the work chambers which are connected to the first pressure medium connection alternate with those connected to the second pressure medium connection, and at least one work chamber is connected to a pressure compensation element. The pressure compensation element is formed by a pressure limiting valve which opens in a direction of the work chamber with the lower working pressure so that pressure medium can overflow from at least one work chamber of a first group into a work chamber of the second group.
The pressure limiting valve opens as a function of the difference in pressure between two work chambers. As a result of a deflecting movement of the wheel, a first work chamber can be discharged and the adjacent chamber compressed. When the pressure falls below a differential pressure, the pressure limiting valve opens even though the working pressure in the compressed work chamber has not yet reached a critical value. In the pressure limiting valve, the opening behavior cannot be different between permissible peak pressures in the compressed work chamber and an instantaneous differential pressure between two adjacent work chambers.
Another proposed solution according to DE 101 40 460 C1 discloses a unit operated by pressure medium that is connected to an external air cushion which is intended to prevent cavitation in a work chamber.
Publication DE 10 2007 009 592 A1 proposes a unit that has a slide element as a pressure compensation element. This slide element controls a system between work chambers in order to counteract peak pressures in the unit due to volume displacement of pressure medium. The slide element cooperates with elastomer springs which are supposed to suppress an impact noise in the swivel motor shaft. However, trials have shown that the elastomer spring is very highly loaded and, as a consequence, is destroyed in some cases.